Wave guide attenuator



Oct: 9, 1951 w. A. JOERNDT 2,570,814

WAVE GUIDE ATTENUATOR Filed Oct. 8, 1948 2 Sheets-Sheet 1 INVENTOR.

WILBUR A. JOERNDT ATTORNEY Oct. 9, 1951 I w. A. JOERNDT 2,570,814

WAVE GUIDE ATTENUATOR Filed Oct. 8, 1948 2 Sheets-Sheet 2 X22 k I6 W fifi ii INVENTOR.

WILBUR A. JOERNDT ATTORNEY Patented Oct. 9, 1951 UNITED STATES PATENT OFFICE WAVE GUIDE ATTENUATOR Wilbur A. Joerndt, Silver Spring, Md., assignor to the United States of America as represented by the Secretary of the Navy Application October s, 1948, Serial No. 53,543

4 Claims.

vention relates to a wave guide attenuator for use with a radar receiver, mounted in a guided missile, which will insure a reduced received signal, from a radar transmitter, concurrent with the launching of the missile and a, maximum signal immediately thereafter.

Many devices have been used in the past to protect the sensitive detector crystal of a radar receiver from damage from signals received in the immediate proximity of the signal source, these chiefly being devices for reducing the value of incoming signals at the launching of a guided missile and providing a subsequent gradual increase in signal amplitude as the missile leaves the vicinity of the radar transmitter. While these attenuators have enjoyed partial success they have not been entirely satisfactory in their operation or results.

In the control of certain guided missiles, a crystal detector is used to receive radar signals from a ground transmitter. This crystal detector is usually incorporated in a wave guide section on the inboard side of a lens type antenna or receiving horn, which is in turn mounted on the guided missile. To provide adequate control, sig- -nals from the ground transmitter to the detector crystal should be available concurrently with the launching of the missile. This received signal must be of such strength to control the flight of the missile at great distances, that when the missile is in the proximity of the transmitter, incident to launching, it is far too strong for the detector crystal and damage to said crystal is likely to occur. It follows, therefore, that incident to said launching, the signal strength must be reduced in order to prevent overloadin of the detector crystal; however, due to the great acceleration of the missile, the received signal must be at its full strength shortly after launching.

An object of the present invention, therefore, is to provide simplified means for attenuating an input radar signal by reducing the amplitude thereof with respect to a receiving detector crystal. Another object is to provide means for attenuating strong radar signals entering a guided missile detector crystal while the said missile is in the vicinity of the transmitter. A further object is to provide a means for attenuating strong radar signals, from a transmitter to a recipient detector crystal located on 9, guided missile, incident to the launching of said missile and subsequently instantaneously removing the attenuating means when the missile has reached an adequate distance from the transmitter and thereby providing a control signal of full strength.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Fig. 1 is an enlarged sectional .view of a preferred form of apparatus embodying the invention, on the plane l-l of Fig. 2, partially in elevation and showing a cooperating wave guide in dash-dot lines;

Fig. 2 is an enlarged vertical section, on the plane 2-2 of Fig. 1, partially in elevation and showing the impeding element in its full attenuating position;

Fig. 3 is a front elevation, on an enlarged scale and partially in section, illustrating the device with the impeding element in its non-attenuating position; and

Fig. 4 is an enlarged side elevation partially in section showing the invention in its non-attenuating position.

Referrin now to the drawings in detail, solely by way of example, and more specifically to Fig. 1, there is shown a section of rectangular shaped wave guide ID, of an appropriate length, and secured thereon, as by brazing, are the conventional wave guide connectin flanges H and I2, positioned to provide smooth, or flush, end surfaces l3 and M respectively. A spacer plate i5, and a base plate IS, with the horizontal leg I! of an angle bracket I8 interposed between them, are secured to the upper edges IQ of the wave guide connecting flanges II and I2, illustrated here as by screws 20.

Located centrally of and integral with the base plate [6, and supported thereby, is a tubular housing 22. A piston 23 is slidably disposed within the axial bore 24 of the housing 22 and has a central portion 25, and end shafts 2'6 and 21 of a reduced diameter and forming the shoulders 28 and 29 at the ends of said portion. A compression spring 30 is arranged within the bore 24 and surrounds the shaft 26 of the piston 23 with the lower end of said spring, suitably shaped, resting on the upper face of the spacer higher or lower decibel value of attenuation, as' desired. The element 3| also comprises a coping member or ferrule 33, attached to the said blade portion 32, as by flush rivets 34. The attenuating element 3| is held in the slot 26a of the shaft 26,

as by the machine screw 35, and when the device is in its full attenuating position, as seen in Figs,

1 and 2, it extends down into the wave guide through a slot 36 in the upper side thereof.

As clearly seen in Fig. 4, when the attenuating element 3| is in its non-attenuating position, fully withdrawn from the wave guide H3, it is received in the slot 31 provided in the wave guide flanges H and I2, and communicating with the slot 36 in said wave guide.

The piston releasing mechanism, consists of a small solenoid 38 mounted on the vertical leg 39 of an angle bracket I 8' so that, as shown in Fig. 2, when the solenoid is unenergized its plunger 4!! extends through a hole 41 in the housing 22' and coacts with the upper shoulder 28 of the enlarged cylindrical body of the piston 23 to retain the element 3! in its attenuating positionwithin the wave guide l0. 1

The upper piston shaft 21 is slotted at 42 to receive an extension shaft 43, here shown fragmentarily, said shaft being secured within the slot by any convenient means, such as a rivet;

The above described device is installed in a guided missiles radar receiving system between the lens antenna or receiving horn and the detector crystal. The wave guide connecting flanges II and I2 coact with mating flanges within the system, as indicated in Fig. 1 by dash-dot lines.

In operation, the radar receiver, with the improved attenuator thereon, would be installed within the confines of the skin, or outer surface, of the guided missile with only the extension shaft 43 protruding therefrom. Prior to the firing of the missile the attenuator would be triggered, or positioned in its full attenuating position, by simply pushing down on the extension shaft 43, overcoming thereby the spring 30, and allowing the solenoid plunger 40, which normally tends to move into the path of the piston 23 when unenergized to slip in above the shoulder 28 of the piston 23, thus locking the said piston with the resistance element 32 in its maximum attenuating position,.as best seen in Fig. 2, extending fully down into the wave guide l0. Concurrently with the firing of the missile, the radar signal from the ground transmitter is of full length; however, the resistance element 32 within the waveguide ID attenuates the signal prior to its reception by the detector crystal and thereby reduce its strength to a value that will not damage the said detector crystal.

Due to the high initial velocity of the missile on firing, a signal of full strength is immediately necessary for adequate control. In order to insure this full signal as soon after firing as required, the actuating solenoid 38 is energized, by the missiles power source (not shown), simultaneously with the firing of the missile. Upon en,-

4 ergization of the solenoid 38 its plunger 40 is withdrawn from the housing 22, as seen in Fig. 4, whereby the spring powered piston instantly moves upward, instantaneously withdrawing the element 32 from the wave guide [0.

With the resistance element 32 completely removed from the wave guide, as illustrated in Figs. 3 and 4, the radar signal is free from attenuation, thereby allowing a signal of maximum strength to reach the detector crystal.

Obviously many modifications and variations of I the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim; r

1. In a radarsignal attenuator for a guided missilehaving a radar receiver with an antenna connected thereto, in combination, a wave guide section having a pair of' connecting end flanges secured thereon, for interconnecting said wave guide section with said antenna, a piston housing, means 'for mounting said housing on said end flanges, a piston disposed within said housing, an attenuator element secured to one end of said piston; and movable into and out of the wave guide section, means for urging saidfelement into said wave guide section to attenuate a received s n W i e the m ss le is n close pr mity to a dar trans ter a d mean for instantaneously removing said element from the wave guide section immediatelyafter launching said missile,

2. In combination with a radar receiver fora guided missile, a wave guide section having a slot therein, a pair of connecting end flanges secured on said wave guide section intereconnecting said section with the radio receiver in said guided missile, a piston housing, means for mounting said housing on'said end flanges, a springactw ated main piston body disposed within saidhousJ- ing, a lower pistonshaft of a diameter smaller than the said piston body and integral therewith, an attenuator element secured to the end'of said shaft and'insertable through the slot in the wave guide section to attenuate a received signal while the missile is in'close proximity to a radar trans}- mitter, and means for instantaneouslywithdraw ing said element from the wave guide section immediately after launching said guided missile.

3. In a radar signal attenuator to be used between a receiving antenna and a crystal detector on a guided missile, a section of rectangular wave guide having a slot therein, a pair of connecting end flanges secured thereon, a piston housing, ,a mounting plate secured thereto, means forsecur ing said plate to the said connecting end f anges, .a piston slidably disposed within said housing and. having a main body. portion, an upper piston shaft of a diameter less than that of. said main body portionand integral therewith and forming a shoulder thereon, a lower piston shaft of a diameter less than that of the said main body portion and integral therewith and providing a shoulder thereon, a spring surround-ing said ing means immediately after the missile has left said vicinity. REFERENCES CITED 4. In apparatus of the Character described as The following references are of record in the recited in claim 3, wherein said attenuating elefil f this patent;

ment latching means includes an electrical 5 solenoid, a plunger extending therefrom and en- UNITED STATES PATENTS gaging the upper shoulder of the spring pressed Number Name 7 Date main body portion of said piston when the at- 1,158 Hollinesworth et b. 1 49 tenuating element is in its full attenuating posi- OTHER REFERENCES tion, and means for energizing said solenoid to in disengage Said plunger from Said shoulder. Practical Analysis of Ultra High Frequency, by

J. R. Meagher and H. J. Markley, copyright 1943, WILBU A JOERNDT, 2nd ed., RCA Service 00., p. 1'7. 

